1. Field of the Invention
The present invention relates to information processing units, such as mobile phones including a PHS (Personal Handyphone System), equipped with a fingerprint sensor and operation keys.
2. Description of the Related Art
Recently, mobile phones have spread at a remarkable pace and have developed as portable information processing units which are equipped with multiple functions including not only simple telephone functions, but also e-mail functions and enhanced memory functions for storing various personal information such as telephone numbers.
Big problems posed by such development of mobile phones include illegal use of mobile phones and unauthorized outflow of information stored in mobile phones.
One of the conventional techniques used to solve these problems involves enabling the use of the mobile phone only when a registered personal identification number is entered.
Because it is troublesome to enter a personal identification number, mobile phones which are equipped with a fingerprint sensor and are enabled only when a registered fingerprint is detected have recently been proposed and actually put on the market (see, for example, Patent Documents 1 and 2). The fingerprint sensor is on a considerably high level in terms of prevention of illegal use and convenience of handling.
Although it is desirable from a security standpoint to mount a fingerprint sensor on mobile phones, under circumstances where there is demand for size and weight reduction of mobile phones and the mobile phones have been downsized close to the limit considering the operability for users, the question is what fingerprint sensor to mount and in what part of the mobile phones.
Operation keys and a screen essential for the mobile phones are laid out in such a way as to face the user simultaneously under normal use so that the user can operate the operation key by looking at the screen. Although it is conceivable to install the fingerprint sensor in a space provided on the back face opposite the front face which contains the operation keys and screen, the fingerprint sensor functions as a kind of operation key operated by the user and installing the fingerprint sensor on the back face sacrifices the operability.
Japanese Patent Laid-Open No. 2002-216116 and Japanese Patent Laid-Open No. 2002-279412 propose the use of a fingerprint sweep sensor which reads a fingerprint as the user moves a finger at right angles to a line sensor consisting of minute sensors arranged one-dimensionally.
The fingerprint sweep sensor does not require much installation space and can be installed on the front face of the mobile phone without increasing the size of the mobile phone, as shown in Japanese Patent Laid-Open No. 2002-216116 and Japanese Patent Laid-Open No. 2002-279412. Japanese Patent Laid-Open No. 2002-216116 shows a drawing in which the fingerprint sweep sensor is installed adjacent to the operation keys while Japanese Patent Laid-Open No. 2002-279412 shows a drawing in which the fingerprint sweep sensor is installed adjacent to the screen.
However, if the fingerprint sweep sensor is installed adjacent to the operation keys without taking any measures, there is a danger of pressing operation keys adjacent to the fingerprint sensor by mistake when moving the finger along the fingerprint sensor. Also, if the fingerprint sensor is installed adjacent to the screen, that part of the screen which is adjacent to the fingerprint sensor may become dirty by being touched by fingertips. However, installing the fingerprint sensor on that part of the mobile phone surface which is distant from the operation keys and screen to prevent the above problems would go counter to the demand for size reduction of the mobile phone.
Also, the fingerprint sweep sensor, which does not require much installation space, can be installed on a flank portion of the mobile phone. In that case, however, the problem of operability remains, as is the case when the fingerprint sensor is installed on the back face. The above problems are not specific to mobile phones, but are common to information processing units equipped with a fingerprint sensor and operation keys.
In view of the above circumstances, the present invention has an object to provide an information processing unit which is equipped with a fingerprint sensor and reconciles size reduction with operability at a high level.